1. Field of the Invention
The present invention relates to a focal plane shutter for digital still cameras having one shutter blade.
2. Description of the Related Art
Among focal plane shutters for digital still cameras, there is a shutter including only one shutter blade composed of a plurality of arms, each with one end pivoted on a base board, and at least one blade pivoted on these arms. The shutter blade opens/closes an opening of an imaging optical path by the reciprocating rotation of a drive member which is connected to one of the arms via a drive pin. It has been known that the drive member uses a set member linked to a motor for rotation in one direction while using an urging force of a spring in the other direction. The reciprocating rotation only by a motor has become of interest lately. Then, as a device advanced further than this, a drive device in that a drive member is integrated with a motor rotor is disclosed in Japanese Unexamined Patent Application Publication No. 2002-287210.
The drive device disclosed in this Publication is suitable for miniaturization, and is very effective for space-saving of the inside of a camera. However, in view of manufacturing, it is not necessarily favorable. The drive member usually operates at a considerable high speed, and upon stopping, it abuts a stopper so as to receive a large impact therefrom. Hence, the rotor requires large motive power and must withstand such large impact. In the drive device disclosed in Japanese Unexamined Patent Application Publication No. 2002-287210, since motor components are assembled on the shutter base board one by one, its performance inspection must be carried out after the shutter assembling. If a drive device fails in the inspection, the motor components must be disassembled and then reassembled, resulting in very troublesome operation and high cost.
If only this problem is taken into consideration, it becomes rather advantageous to use a general-purpose motor so as to drive an independent drive member as usual. However, when such a general-purpose motor is used, since a transmission mechanism to the drive member is complicated, the entire drive device becomes large in size, and although the motor itself is inexpensive, the entire cost is pushed up.